Synthesis and Initial Characterization of a Calcium-Deficient Hydroxyapatite-Bacterial Cellulose Composite

Bacterial cellulose is a biopolymer currently being investigated for use in a variety of biomedical applications. It has high purity, extensive hydrophilicity, and superior mechanical properties. A novel composite was developed consisting of bioceramic particles precipitated in bacterial cellulose. Alizarin Red S staining was first used to indicate the presence of calcium. Laser-Induced Breakdown Analysis confirmed the presence of calcium and phosphorus in the cellulose matrix. X-ray diffraction was finally used to identify the precipitated minerals. Incubating the cellulose in aqueous calcium chloride followed by incubation in sodium phosphate dibasic produced calcium-deficient hydroxyapatite. Incubation in calcium chloride and sodium carbonate solutions produced calcium carbonate. Bacterial cellulose was incubated in simulated body fluid to ascertain how it would react in an artificial physiological environment. In-vitro testing with osteoblasts was also conducted to assess its biocompatibility. By performing cell counts and an alkaline phosphatase assay, it was proven that the osteoblasts preferentially attached to the hydroxyapatite bacterial cellulose versus native bacterial cellulose. The bacterial cellulose- hydroxyapatite composite is synthesized by incubation in aqueous salt solutions at physiological pH and ambient temperature. This contrasts other hydroxyapatite synthesis methods that use harsh chemicals (e.g. orthophosphoric acid) at extreme temperature or pressure conditions (hydrothermal reactions at 275ºC / 12000 psi). Combining hydroxyapatite into bacterial cellulose may generate a composite with favorable mechanical and chemical properties that are appropriate for various medical applications.